My Favorite Mistake
by HP Slash Luv
Summary: AU where Luna was born in the Marauder's era. Luna walks in on her boyfriend, Barty, having sex with their friend, Regulus. Her response is different than either boy expected it to be.


**Title:** My Favorite Mistake  
 **Rating:** M  
 **Pairing(s)/Character(s):** Regulus/Luna/Barty  
 **Warnings:** sexual content, infidelity  
 **Disclaimer:** Don't own 'em - not making any money off 'em. Dern it.  
 **Word Count:** 1,053  
 **Summary:** AU where Luna was born in the Marauder's era. Luna walks in on her boyfriend, Barty, having sex with their friend, Regulus. Her response is different than either boy expected it to be.

 **Notes:**

 **Year Long Scavenger Hunt Challenge and Competition:** B10. (character) Regulus Black

 **Hogwarts School of Witchcraft & Wizardry: **Writing Club - Title (My Favourite Mistake)

 **Crystals, Gemstones & Astrology:** Lapis Lazuli/Expert - Write about someone finding their partner having intercourse with someone else. (1,000-4,000 words)

* * *

Barty knew this was wrong, but as Regulus's mouth engulfed him, Barty forgot his own name. He gasped, fingers tangling in Regulus's long black strands, pushing himself deep inside the warm and inviting mouth.

He knew if Regulus kept up with his talented tongue, Barty wouldn't be able to contain himself, and he wanted to come while Regulus was inside of him.

He pulled on the hair, wordlessly getting his meaning across.

Regulus smirked as he let go of Barty's erection with a loud pop. "I know what you need," he huskily whispered.

Barty nodded. "Please."

Regulus slithered up his body and with deft fingers, quickly prepared Barty. He quickly entered Barty, not giving either of them any time to rethink their actions and the possible consequences of said actions.

Barty moaned, feeling so unbelievably full.

Regulus panted harshly, lips touching Barty's shoulders, and he slowly pulled out to the tip, before he thrust back in.

The pace started out slowly, but soon, it sped up.

There was nothing but moans and pants in the otherwise silent room. Neither of them heard the door opening, but somehow, they managed to hear the soft gasp.

Both of them turned to the doorway, rhythm faltering at the sight of a familiar ethereal blonde, but they were both too close to stop their bodies. And with Luna Lovegood—Barty's girlfriend and Regulus's best friend—watching, they reached their orgasms together.

They both sat up, but neither of them moved to cover themselves. They knew it wouldn't help the situation. "Luna," Barty breathed.

"We can explain," Regulus began.

Luna shook her head. "No, you don't have to."

"Luna, I love you," Barty tried desperately. "I really do," he stated, hoping the extra emphasis would help Luna believe the truth of his words.

Surprisingly, Luna smiled softly and looked at Barty. "I do believe you." She turned her all-knowing gaze to Regulus. "Just like I believe you care about me as well."

"I do," Regulus agreed.

Luna took a step closer to the bed, not seeming too bothered by the way their bodies stiffened as she closed in on them. "I also know you two care about each other, and I had a feeling that you would eventually fall into bed with each other."

Barty blinked at her easy admission. "And how is it that you seem fine with that? Shouldn't you be yelling, declaring us over? Telling me you never want to see me or my cheating face again?"

She raised her eyebrows. "Is that what you want?"

"Of course not," Barty erupted. "I love you just as much as I always have. But how can you possibly be okay with the idea that I also have feelings for Regulus? You shouldn't be okay with that. You should hate me for it. Why don't you?"

Regulus had decided to stay silent, but even he couldn't help himself. "Why don't you hate me? I helped your boyfriend cheat on you. How can you still look at me with such kind eyes and a gentle smile?"

"Because I do know you both care about me, and neither of you wanted to hurt me. You simply couldn't control your feelings any longer. How can I fault the two of you for loving each other? To me, love is precious, and it should never be hated, no matter the form it comes in."

Regulus looked at Barty. "Barty, do you remember what we talked about..."

"Yes, and until now, I didn't believe it was possible."

"You didn't believe what was possible?" Luna questioned.

Regulus nodded at Barty. Since Barty was the boyfriend, he should be the one to broach the subject.

Barty took a deep breath. "Luna, I love you, and I don't want to stop being with you."

"I don't want that either," Luna answered. "We'll work it out. You'll be allowed to have both of us."

Barty leaned forward and pressed his lips against hers. When he slowly pulled away after savoring the taste of apple that seemed to be permanently stained on her lips, he whispered, "It doesn't simply have to be you sharing me."

Luna had a knowing twinkle in her eyes, and Barty wouldn't have been surprised if she already figured out where he was going with that statement. "Oh really?"

Regulus took over despite the decision that Barty should do the talking. He cupped Luna's cheek, turning her face so she now looked at him. He leaned forward and pressed his lips against hers.

Luna's panting was just a bit heavier when he pulled back.

Regulus couldn't help his self-satisfaction that he got that kind of reaction out of her. He licked his lips. "Barty was right; you _do_ taste like apples."

Luna blinked.

Regulus continued, "You're so beautiful." His thumb rubbed her lips, and he groaned when she automatically parted her lips. "I don't love you the way I love Barty, but I am attracted to you, and I think if I let myself, I could easily fall in love with you. The real question is do you think you could ever fall in love with me?"

Luna pulled away slightly and looked from one boy to the other. Her heart flipped outrageously when she looked at Barty, and it did another flip, albeit tinier, when her gaze landed on Regulus. It made her answer easy. "Yes, I think I could," she admitted.

Regulus and Barty had identical grins on their handsome faces. Both leaned closer to her and pressed their lips against her neck. She sighed, allowing herself to be pulled fully onto the bed, and then pushed to lay down against the pillows.

Both simultaneously worked to divest her of all of her clothes, and she simply allowed it, enjoying their attention.

Barty took a step back so he could watch Regulus pleasure Luna and had never seen anything sexier.

Cheating on Luna had been a mistake. Honesty about his feelings would have been the better choice, but it was Barty's favorite mistake to date.

And it didn't hurt that he had such an awesome and open-minded girlfriend.

When Luna's cries got louder, signaling her release was pending, Barty jumped back into the fray, taking her left breast into his mouth. After all, he couldn't let Regulus have _all_ the fun, right?


End file.
